I downloaded lots of Graflex and a coupla Kodak catalogs and found out this
paraphrased "the 5x7 auto differs from the 4x5 , having a hinged front as well as a door.."
From the excellent pictures, I conclude that the secret button worked against a flat spring that caught the metal thingy shown attached to the front flap bottom with two screws.
And I'll take all the 35/125 I can get in lieu of mm
As for the door....to try to replicate it, or to make it from round cornered Altoids tins and have it flip to 90 degrees out, as a lens shade?
Since i won't be able on several levels to restore the leather, I'm tempted to sand the bare wood and Urethane it, and paint the new front flap "blue and let it happen"- an old architect joke.
Northwest NSW? Is that the big blank spot on maps ?
Thanks a lot more

As the 1/16" is measured with the plastic rule I've had since high school the actual measurement could well be one of the other fractions you mentioned

Ed,

I live in Coffs Harbour, northern New South Wales, which is on the east coast. It has a few more people that the north west! Good luck with the project and keep us posted. By the way cameraleather.com might have the leather you are looking for.